1. Field of the Invention
The present invention relates to a molten metal supply system and, more particularly, a continuous pressure molten metal supply system and method for forming continuous metal articles of indefinite length, and further to a dual action valve suitable for use in molten metal applications generally and the continuous pressure molten metal supply system in particular.
2. Description of the Prior Art
The metal working process known as extrusion involves pressing metal stock (ingot or billet) through a die opening having a predetermined configuration in order to form a shape having a longer length and a substantially constant cross-section. For example, in the extrusion of aluminum alloys, the aluminum stock is preheated to the proper extrusion temperature. The aluminum stock is then placed into a heated cylinder. The cylinder utilized in the extrusion process has a die opening at one end of the desired shape and a reciprocal piston or ram having approximately the same cross-sectional dimensions as the bore of the cylinder. This piston or ram moves against the aluminum stock to compress the aluminum stock. The opening in the die is the path of least resistance for the aluminum stock under pressure. The aluminum stock deforms and flows through the die opening to produce an extruded product having the same cross-sectional shape as the die opening.
Referring to FIG. 1, the foregoing described extrusion process is identified by reference numeral 10, and typically consists of several discreet and discontinuous operations including: melting 20, casting 30, homogenizing 40, optionally sawing 50, reheating 60, and finally, extrusion 70. The aluminum stock is cast at an elevated temperature and typically cooled to room temperature. Because the aluminum stock is cast, there is a certain amount of inhomogeneity in the structure and the aluminum stock is heated to homogenize the cast metal. Following the homogenization step, the aluminum stock is cooled to room temperature. After cooling, the homogenized aluminum stock is reheated in a furnace to an elevated temperature called the preheat temperature. Those skilled in the art will appreciate that the preheat temperature is generally the same for each billet that is to be extruded in a series of billets and is based on experience. After the aluminum stock has reached the preheat temperature, it is ready to be placed in an extrusion press and extruded.
All of the foregoing steps relate to practices that are well known to those skilled in the art of casting and extruding. Each of the foregoing steps is related to metallurgical control of the metal to be extruded. These steps are very cost intensive, with energy costs incurring each time the metal stock is reheated from room temperature. There are also in-process recovery costs associated with the need to trim the metal stock, labor costs associated with process inventory, and capital and operational costs for the extrusion equipment.
Attempts have been made in the prior art to design an extrusion apparatus that will operate directly with molten metal. U.S. Pat. No. 3,328,994 to Lindemann discloses one such example. The Lindemann patent discloses an apparatus for extruding metal through an extrusion nozzle to form a solid rod. The apparatus includes a container for containing a supply of molten metal and an extrusion die (i.e., extrusion nozzle) located at the outlet of the container. A conduit leads from a bottom opening of the container to the extrusion nozzle. A heated chamber is located in the conduit leading from the bottom opening of the container to the extrusion nozzle and is used to heat the molten metal passing to the extrusion nozzle. A cooling chamber surrounds the extrusion nozzle to cool and solidify the molten metal as it passes therethrough. The container is pressurized to force the molten metal contained in the container through the outlet conduit, heated chamber and ultimately, the extrusion nozzle.
U.S. Pat. No. 4,075,881 to Kreidler discloses a method and device for making rods, tubes, and profiled articles directly from molten metal by extrusion through use of a forming tool and die. The molten metal is charged into a receiving compartment of the device in successive batches that are cooled so as to be transformed into a thermal-plastic condition. The successive batches build up layer-by-layer to form a bar or other similar article.
U.S. Pat. Nos. 4,774,997 and 4,718,476, both to Eibe, disclose an apparatus and method for continuous extrusion casting of molten metal. In the apparatus disclosed by the Eibe patents, molten metal is contained in a pressure vessel that may be pressurized with air or an inert gas such as argon. When the pressure vessel is pressurized, the molten metal contained therein is forced through an extrusion die assembly. The extrusion die assembly includes a mold that is in fluid communication with a downstream sizing die. Spray nozzles are positioned to spray water on the outside of the mold to cool and solidify the molten metal passing therethrough. The cooled and solidified metal is then forced through the sizing die. Upon exiting the sizing die, the extruded metal in the form of a metal strip is passed between a pair of pinch rolls and further cooled before being wound on a coiler.
A primary object of the present invention is to provide a dual action valve suitable for use in molten metal applications generally and for use, in particular, in a molten metal supply system and method capable of forming continuous metal articles of indefinite lengths as described herein.
The above object is generally accomplished by a dual action valve for molten metal applications, which may be used, for example, as part of a molten metal supply system as set forth in this disclosure. The dual action valve generally comprises a housing defining an inlet opening, a valve body disposed within the housing, an inlet float member, and an outlet float assembly. The valve body defines an inlet conduit in fluid communication with the inlet opening for receiving molten metal into the valve body and an outlet conduit for dispensing molten metal from the valve body. The inlet float member is disposed in the inlet conduit and movable with molten metal flow into the valve body to open the inlet conduit. The inlet float member is adapted to close the inlet conduit upon termination of molten metal flow into the valve body. The outlet float assembly is disposed in the outlet conduit and movable with molten metal flow in the outlet conduit to permit molten metal outflow from the valve body and prevent reverse molten metal flow in the outlet conduit.
The dual action valve may further include an inlet seat liner disposed in the inlet conduit. The inlet float member preferably coacts with the inlet seat liner to close the inlet conduit upon termination of molten metal flow into the valve body. The inlet seat liner may comprise a tapered outer surface cooperating with a tapered recessed portion of the inlet conduit.
The inlet float member may have a greater density than the molten metal admitted to the valve body, such that the inlet float member closes the inlet conduit under the force of gravity upon termination of molten metal flow into the valve body. The inlet float member may be spherical shaped.
The outlet float assembly may comprise a carrier member and an outlet float member support by the carrier member. The outlet float member may have a lower density than the molten metal admitted to the valve body, such that the outlet float member is buoyed up from the carrier member to close the outlet conduit if reverse molten metal flow occurs in the outlet conduit. Additionally, the carrier member and outlet float member may have a combined density lower than the molten metal admitted to the valve body, such that the carrier member and outlet float member are buoyed up together to close the outlet conduit if reverse molten metal flow occurs in the outlet conduit. Further, the carrier member and outlet float member may be formed integrally as a one-piece unit.
The outlet float member may be spherical shaped. The outlet float member may be removably supported by the carrier member. For example, the outlet float member may be removably received in a cup-shaped recess defined in the carrier member. The outlet float member and the cup-shaped recess may have mating spherical shapes.
The outlet conduit may define an outlet chamber, and the carrier member and outlet float member may be disposed in the outlet chamber. The carrier member may define a central passage in fluid communication with the outlet chamber for passage of molten metal through the outlet chamber. The carrier member may further define a plurality of branch conduits connecting the central passage to the outlet chamber. The carrier member may further define a pressure seal port connecting the cup-shaped recess and central passage for molten metal fluid communication therebetween.
An outlet seat liner may be disposed in the outlet conduit immediately upstream of the outlet chamber. The outlet float member may coact with the outlet seat liner to close the outlet conduit upon reverse molten metal flow in the outlet chamber. The outlet seat liner may comprise a tapered outer surface cooperating with a tapered recessed portion of the outlet conduit.
Top and bottom ends of the housing may be provided with circumferential seal grooves for creating seals with molten metal flow conduits to be connected to the top and bottom ends of the housing.
Additionally, the dual action valve may further comprise a spring member disposed in the inlet conduit downstream upstream of the inlet float member. The spring member may be adapted to coact with the inlet float member to assist in closing the inlet conduit upon termination of molten metal flow into the valve body. The outlet float assembly may further comprise a second spring member adapted to coact with the carrier member to assist in closing the outlet conduit if reverse molten metal flow occurs in the outlet conduit. Only one spring member provided in the inlet or outlet conduit wherein either the inlet float member or the outlet float assembly is working against the force of gravity is preferably required in the dual action valve in accordance with the present invention, as discussed further herein.
Further details and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the drawings, wherein like parts are designated with like reference numerals.